Source of green donuts for instrument tubing installation?

None of the usual suspects online produce results - or I don't search using correct terms.

Did you try "castration rings?"

On Friday, April 6, 2018 at 1:49:23 PM UTC-4, Movses Babayan wrote:
None of the usual suspects online produce results -
or I don't search using correct terms.

https://www.fleetfarm.com/detail/syr...MaAnt6EALw_wcB

Did you search for "rubber grommets"?

Available from Farm Supply stores, veterinarians, Tractor Supply stores.
Note: I use them, but out here in the high desert, where double-digit humidity is the exception, not the norm, the rubber donuts dry out and crack after a few months. But then, considering their intended purpose, longevity is not a part of the design.

On Friday, April 6, 2018 at 12:02:45 PM UTC-7, wrote:
Available from Farm Supply stores, veterinarians, Tractor Supply stores.
Note: I use them, but out here in the high desert, where double-digit humidity is the exception, not the norm, the rubber donuts dry out and crack after a few months.

Fuel injector O-rings might work; they tend towards large cross-sections and small IDs.

I dont use the docking rings anynore, after a few years they deteriorate to mush. I now use a short length
of silicon tube that fits over the instrument tube, a much better lasting material, and cheap.
Dave

On Friday, April 6, 2018 at 4:55:52 PM UTC-7, wrote:
I dont use the docking rings anynore, after a few years they deteriorate to mush. I now use a short length
of silicon tube that fits over the instrument tube, a much better lasting material, and cheap.
Dave

Silicone is a good choice. If you prefer O-rings, though you cannot always go by color, green ones are used in auto air conditioning system seals and indicate HNBR. This would be a particularly good rubber for glider tubing "clamps" as well. See the link for HNBR characteristics:

http://www.mantaline.com/capabilitie...e/hnbr-rubber/

bumper

Is there a particular reason to use donuts or anything similar at all for instrument installation? Just push the tube to pneumatic port and go flying.

Using them prevents leaks later on, clamping the tubes.